Aperiodic Disturbance Rejection in Repetitive-Control Systems

A repetitive control system (RCS) provides good control performance for periodic signals, but it may not satisfactorily reject aperiodic disturbances. Our solution is an equivalent-input-disturbance (EID)-based RCS in which aperiodic disturbances are estimated by an EID estimator and rejected by incorporation of the estimate into the repetitive control law. A stability criterion and a design algorithm have been developed, and the validity of the method has been demonstrated through simulations and experiments on a rotational speed control system. A comparison of the disturbance rejection performance of this method, proportional-integral-differential control, conventional repetitive control, and H_∞ repetitive control demonstrates the superiority of this method.